fork: fix error handling in dup_task()
The function dup_task() may fail at the following function calls in the
following order.
0) alloc_task_struct_node()
1) alloc_thread_info_node()
2) arch_dup_task_struct()
Error by 0) is not a matter, it can just return. But error by 1) requires
releasing task_struct allocated by 0) before it returns. Likewise, error
by 2) requires releasing task_struct and thread_info allocated by 0) and
1).
The existing error handling calls free_task_struct() and
free_thread_info() which do not only release task_struct and thread_info,
but also call architecture specific arch_release_task_struct() and
arch_release_thread_info().
The problem is that task_struct and thread_info are not fully initialized
yet at this point, but arch_release_task_struct() and
arch_release_thread_info() are called with them.
For example, x86 defines its own arch_release_task_struct() that releases
a task_xstate. If alloc_thread_info_node() fails in dup_task(),
arch_release_task_struct() is called with task_struct which is just
allocated and filled with garbage in this error handling.
This actually happened with tools/testing/fault-injection/failcmd.sh
# env FAILCMD_TYPE=fail_page_alloc \
./tools/testing/fault-injection/failcmd.sh --times=100 \
--min-order=0 --ignore-gfp-wait=0 \
-- make -C tools/testing/selftests/ run_tests
In order to fix this issue, make free_{task_struct,thread_info}() not to
call arch_release_{task_struct,thread_info}() and call
arch_release_{task_struct,thread_info}() implicitly where needed.
Default arch_release_task_struct() and arch_release_thread_info() are
defined as empty by default. So this change only affects the
architectures which implement their own arch_release_task_struct() or
arch_release_thread_info() as listed below.
arch_release_task_struct(): x86, sh
arch_release_thread_info(): mn10300, tile
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Salman Qazi <sqazi@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index 088025b..8efac1f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -114,6 +114,10 @@
return total;
}
+void __weak arch_release_task_struct(struct task_struct *tsk)
+{
+}
+
#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
static struct kmem_cache *task_struct_cachep;
@@ -122,17 +126,17 @@
return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
}
-void __weak arch_release_task_struct(struct task_struct *tsk) { }
-
static inline void free_task_struct(struct task_struct *tsk)
{
- arch_release_task_struct(tsk);
kmem_cache_free(task_struct_cachep, tsk);
}
#endif
+void __weak arch_release_thread_info(struct thread_info *ti)
+{
+}
+
#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
-void __weak arch_release_thread_info(struct thread_info *ti) { }
/*
* Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
@@ -150,7 +154,6 @@
static inline void free_thread_info(struct thread_info *ti)
{
- arch_release_thread_info(ti);
free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
# else
@@ -164,7 +167,6 @@
static void free_thread_info(struct thread_info *ti)
{
- arch_release_thread_info(ti);
kmem_cache_free(thread_info_cache, ti);
}
@@ -205,10 +207,12 @@
void free_task(struct task_struct *tsk)
{
account_kernel_stack(tsk->stack, -1);
+ arch_release_thread_info(tsk->stack);
free_thread_info(tsk->stack);
rt_mutex_debug_task_free(tsk);
ftrace_graph_exit_task(tsk);
put_seccomp_filter(tsk);
+ arch_release_task_struct(tsk);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
@@ -298,14 +302,12 @@
return NULL;
ti = alloc_thread_info_node(tsk, node);
- if (!ti) {
- free_task_struct(tsk);
- return NULL;
- }
+ if (!ti)
+ goto free_tsk;
err = arch_dup_task_struct(tsk, orig);
if (err)
- goto out;
+ goto free_ti;
tsk->stack = ti;
@@ -333,8 +335,9 @@
return tsk;
-out:
+free_ti:
free_thread_info(ti);
+free_tsk:
free_task_struct(tsk);
return NULL;
}
